1. Field of the Invention
The present invention relates to an optical deflector capable of deflecting an input beam three-dimensionally and outputting the deflected beam.
2. Description of the Related Art
Technology for deflecting light beams is used in many fields, in devices such as scanning electron microscopes, laser printers, bar-code scanners, optical cross-connects, and so on.
Known methods of deflecting light beams make use of rotating mirrors, the acousto-optic effect, and the electro-optical effect. The optical cross-connects used in optical communication, for example, employ micro-electromechanical systems (MEMS) with micromirrors. These optical cross-connects are capable of switching up to a thousand channels by mechanically controlling the tilt angles of the micromirrors.
The optical deflectors implemented by MEMS technology, however, require mechanical driving of a mirror. Accordingly, it is impossible to shorten the switching time to less than about one millisecond (1 ms).
Deflection devices that operate by using the electro-optical effect are intrinsically faster. Known examples of such devices are disclosed in U.S. Pat. No. 6,449,084 to Guo and U.S. Pat. No. 6,947,625 to Nishizawa et al. A more recent technique deflects an optical beam by injecting a space charge into a dielectric body to create a refractive index distribution aligned with the resulting electric field, as described by Nakamura et al. in ‘Wide-angle, low-voltage electro-optic beam deflection based on space-charge-controlled mode of electrical conduction in KTa1-xNbxO3’, Applied Physics Letters 89, 131115 (2006).
A problem common to these known electro-optical deflectors is that they can only deflect light beams two-dimensionally, in a single plane including the incident beam.